As winters slowly approach parts of north India, the peak pollution season is also expected to return to some major cities across the country.
A new report from Respirer Reports, an initiative of Respirer Living Sciences, a climate sciences IoT startup based out of Mumbai and Pune, analyzed the air quality trends in India’s most and least polluted cities over the last year: 1 October 2022 and 30 September 2023.
From 1 October, 2023, a revised version of Graded Response Action Plan (GRAP), a government air pollution control programme, has come into force in Delhi and 24 nearby districts, collectively known as the National Capital Region (NCR). The region has several places which frequently top Indian and global air pollution rankings.
According to the findings of the report, in collaboration with Climate Trends – a research-based consulting and capacity building initiative that aims to bring focus on issues of environment, climate change and sustainable development – Delhi and other cities in the NCR region still dominate air pollution rankings. The national captial’s air quality improved marginally, yet it was the most polluted city between 1 October 2022 and 30 September 2023, with a PM2.5 concentration of 100.1 micrograms/cubic metre (μg/m3). This is more than thrice the government’s ‘good’ level and 20 times the World Health Organization’s safe limit.
There are five NCR cities, Delhi, Faridabad, Ghaziabad, Noida and Meerut, and in Bihar, Patna and Muzaffarpur in the top 10 list of polluted cities in India, from 1 October 2022 to 30 September 2023. The list also has Nalbari in Assam, Asansol in West Bengal, and Gwalior in Madhya Pradesh. Currently, Nalbari and Asansol have only one air quality monitor each, while Gwalior has three monitors that record the National Clean Air Programme (NCAP) data.
PM2.5 (fine particulate matter) data is a widely used measure for assessing the impacts of air pollution on health. The data is available through NCAP, which aims to reduce PM2.5 and PM10 concentrations in Indian cities by 40 per cent of 2017 levels by 2026, a press release from Respirer Living Sciences says.
Patna, in second place at 99.7 μg/m3, saw a 24 per cent deterioration in air quality over the previous year. Interestingly, seven cities in the top 10 polluted cities are in Delhi-NCR and Bihar, both part of the Indo-Gangetic Plain. A look at six major capitals, which have air quality challenges, during the peak pollution months (October–March) between 2019 and 2023, shows that Mumbai’s air quality worsened steadily while Delhi’s and Lucknow’s improved.
According to the findings of the report, Aizawl, Mizoram, is the place with India’s cleanest air, with a PM2.5 level of only 11.1 μg/m3.
For the report, the organization studied two sets of air quality data. The first is the government’s PM2.5 data for the past year, i.e., 1 October 2022 to 30 September 2023, to track improvement in air quality over the previous year in NCR and other cities listed in the NCAP. The other is PM2.5 data during winter, roughly October–March, when pollution levels rise. The period of study is from 2019, when NCAP was launched, to 2023 in six major capitals known to have air quality challenges. These are Delhi, Mumbai, Kolkata, Bengaluru, Lucknow and Patna.